AmazonSecurityTokenServiceClient.AssumeRole (AssumeRoleRequest)

Method

Returns a set of temporary security credentials (consisting of an access key ID, a
secret access key, and a security token) that you can use to access AWS resources
that you might not normally have access to. Typically, you use AssumeRole
for cross-account access or federation.

Important: You cannot call AssumeRole by using AWS account credentials;
access will be denied. You must use IAM user credentials or temporary security credentials
to call AssumeRole.

For cross-account access, imagine that you own multiple accounts and need to access
resources in each account. You could create long-term credentials in each account
to access those resources. However, managing all those credentials and remembering
which one can access which account can be time consuming. Instead, you can create
one set of long-term credentials in one account and then use temporary security credentials
to access all the other accounts by assuming roles in those accounts. For more information
about roles, see IAM
Roles (Delegation and Federation) in the Using IAM.

For federation, you can, for example, grant single sign-on access to the AWS Management
Console. If you already have an identity and authentication system in your corporate
network, you don't have to recreate user identities in AWS in order to grant those
user identities access to AWS. Instead, after a user has been authenticated, you call
AssumeRole (and specify the role with the appropriate permissions) to
get temporary security credentials for that user. With those temporary security credentials,
you construct a sign-in URL that users can use to access the console. For more information,
see Common
Scenarios for Temporary Credentials in the Using IAM.

The temporary security credentials are valid for the duration that you specified when
calling AssumeRole, which can be from 900 seconds (15 minutes) to 3600
seconds (1 hour). The default is 1 hour.

Optionally, you can pass an IAM access policy to this operation. If you choose not
to pass a policy, the temporary security credentials that are returned by the operation
have the permissions that are defined in the access policy of the role that is being
assumed. If you pass a policy to this operation, the temporary security credentials
that are returned by the operation have the permissions that are allowed by both the
access policy of the role that is being assumed, and the policy that
you pass. This gives you a way to further restrict the permissions for the resulting
temporary security credentials. You cannot use the passed policy to grant permissions
that are in excess of those allowed by the access policy of the role that is being
assumed. For more information, see Permissions
for AssumeRole, AssumeRoleWithSAML, and AssumeRoleWithWebIdentity in the Using
IAM.

To assume a role, your AWS account must be trusted by the role. The trust relationship
is defined in the role's trust policy when the role is created. You must also have
a policy that allows you to call sts:AssumeRole.

Using MFA with AssumeRole

You can optionally include multi-factor authentication (MFA) information when you
call AssumeRole. This is useful for cross-account scenarios in which
you want to make sure that the user who is assuming the role has been authenticated
using an AWS MFA device. In that scenario, the trust policy of the role being assumed
includes a condition that tests for MFA authentication; if the caller does not include
valid MFA information, the request to assume the role is denied. The condition in
a trust policy that tests for MFA authentication might look like the following example.

To use MFA with AssumeRole, you pass values for the SerialNumber
and TokenCode parameters. The SerialNumber value identifies
the user's hardware or virtual MFA device. The TokenCode is the time-based
one-time password (TOTP) that the MFA devices produces.

STS is not activated in the requested region for the account that is being asked to
create temporary credentials. The account administrator must activate STS in that
region using the IAM Console. For more information, see Activating
and Deactivating AWS STS in an AWS Region in the Using IAM.